Pentagon copying is more impaired in dementia with Lewy bodies than in Alzheimer's disease

Center for Alzheimer Disease and Related Disorders, Department of Neurology, Southern Illinois University School of Medicine,
Springfield, Illinois, USA

Dr T A Ala tala{at}siumed.edu

Received 12 June 2000

Revised 8 November 2000

Accepted 22 November 2000

Abstract

OBJECTIVES In many cases the clinical differentiation of patients with dementia with Lewy bodies (DLB) from those with Alzheimer's disease
(AD) has been difficult. Because many neuropsychological studies have reported greater visuospatial/constructional impairment
in DLB than in AD, it was determined whether accuracy in copying the interlocking pentagons item on the mini mental state
examination (MMSE) may be helpful in distinguishing patients with DLB from those with AD relatively early in the course of
the dementia.

METHODS All cases of neuropathologically proved DLB and AD in the Center for Alzheimer Disease and Related Disorders brain bank were
retrospectively reviewed, and the first available MMSE for each was retrieved. Only patients with MMSE scores⩾13 were included,
indicating mild to moderate dementia. The patients' copies of the interlocking pentagons were analyzed and graded as acceptable
or unacceptable according to the original instructions for grading the MMSE.

RESULTS Seventeen patients with DLB and 27 patients with AD were identified for whom MMSE with copies of the interlocking pentagons
were available. Two patients with DLB (MMSEs 22 and 27) drew the pentagons acceptably, by contrast with 16 of the patients
with AD (MMSEs 13–28). An unacceptable copy was associated with DLB with a sensitivity of 88% and a specificity of 59% (p=0.002).

CONCLUSIONS For patients with MMSE scores⩾13, an inability to accurately copy the pentagons suggests that the diagnosis is more likely
DLB than AD. The results confirm the work of others on visuospatial/constructional impairment in DLB and indicate that this
feature may be helpful in its diagnosis.